The purpose of this research study is to investigate melatonin as a safe method of improving sleep in patients with Parkinson's Disease. People with Parkinson's Disease commonly suffer disturbed sleep, which adversely affects the individual diagnosed with Parkinson's Disease and their caregiver(s). Disturbed sleep is known to increase in both severity and frequency as the disease progresses. Melatonin may help treat this difficult problem. Melatonin is a hormone produced at night by the pineal gland in the brain. Melatonin is believed to help adjust our bodies to a 24-hour daily rhythm and maintain a normal sleep/wake cycle. This research study will investigate whether oral melatonin can improve the sleep cycle in persons with Parkinson's Disease.